1. Field of the Invention
The present invention relates to an indicating circuit, and more particularly, to an indicating circuit for indicating network status.
2. Description of Related Art
There are two types of indicating circuits for indicating network status through indicating units such as LEDs: 1) a first type of indicating circuit indicates the networks according to the combination of two status signals designated Speed and Link, 2) a second type of indicating circuit indicates the network status according to two status signals independent from each other designated 10M/LINK/ACTIVITY and 100M/LINK/ACTIVITY. Referring to FIG. 4, a first type of indicating circuit includes a first type of network IC 10, a NOT gate U1, two LEDs L1, L2, and a resistor Ra. The network IC 10 includes a Speed pin connected to an anode of the LED L1 and an input terminal of a NOT gate. An output terminal of the NOT gate is connected to an anode of the LED L2. A node A between two cathodes of the two LEDs L1, L2 is connected to a Link pin of the network IC 10 through the resistor Ra. The NOT gate U1, the two LEDs L1, L2 and the resistor Ra constitute an indicator circuit. The network IC 10 is set in a kernel board, and the indicator circuit is set in a device board.
Level/value of the Link pin corresponding to the network status, and level/value of the Speed pin corresponding to the network transmitting speed are listed as below:
TABLE 1Network statusLevel/value of Link pinLinkedLow/0Not linkedHigh/1Transmitting and ReceivingAlternating between 0, 1
TABLE 2Network transmitting speedLevel/value of Speed pin 10 MbpsHigh/1100 MbpsLow/0
According to Table 1, value at the Link pin is 0 when the network is “linked”, and is 1 when the network is “not linked”. When the network is “transmitting and receiving”, the value at the Link pin alternates between 0 and 1. According to Table 2, the value at the Speed pin is 1 when the speed of the network is 10 Mbps, and is 0 when the speed of the network is 100 Mbps. So when the network speed is 10 Mbps and the network is “linked”, the LED L1 lights up. When the network speed is 100 Mbps and the network is “linked”, the LED L2 lights up. When the network speed is 10 Mbps and the network is “transmitting and receiving”, the LED L1 blinks. When the network speed is 100 Mbps and the network is “transmitting and receiving”, the LED L2 blinks. When the network is “not linked”, the two LEDs L1 and L2 remain off.
Referring to FIG. 5, a second type of indicating circuit includes a second type of network IC 30, two resistors Rb, Rc, and two LEDs L3, L4. A 10M/LINK/ACTIVITY pin of the network IC 30 is connected to an anode of the LED L3 through the resistor Rb, and a 100M/LINK/ACTIVITY pin of the network IC 30 is connected to an anode of the LED L4 through the resistor Rc. Cathodes of the two LEDs L3 and L4 are grounded. The two resistors Rb and Rc, the two LEDs L3 and L4 constitute an indicator circuit. The network IC 30 is set in a kernel board, and the indicator circuit is set in a device board. When the network speed is 10 Mbps and the network is “linked”, the LED L3 lights up. When the network speed is 100 Mbps and the network is “linked”, the LED L4 lights up. When the network speed is 10 Mbps and the network is “transmitting and receiving”, the LED L3 blinks. When the network speed is 100 Mbps and the network is “transmitting and receiving”, the LED L4 blinks. When the network is “not linked”, the two LEDs L3, L4 remain off.
According to the FIGS. 4 and 5, an indicator circuit is only compatible with a specified network IC, so different indicator circuits are needed corresponding to different network ICs. Sometime the network IC in the kernel board must be changed, and the indicator circuit in the device board must also be changed in accordance with the network IC. However, when specifications of customer orders for the kernel boards change, and current device boards on hand are not compatible with the new order, the device board has to be redesigned and tested, which increases costs and wastes time.
What is needed is an indicating circuit comprising an indicator circuit compatible with different types of network ICs.